This invention relates to cylinder positioners for offset presses and duplicators, and more particularly, to a cylinder positioning apparatus which can be added to, or manufactured with, presses and duplicators to obtain color registration rapidly and efficiently.
In the printing of multicolor images, it is important that the registration of each color where it borders on another color be proper. Fine adjustments must be made to the printing presses to prevent misalignment of the colors, i.e., wherein the colors overlap each other or when there is a gap between the colors.
In most cases, for two-color presses, the operator uses "eyeballing" to adjust the cylinders of the presses. After the plates have been placed upon the first and second color cylinders, the operator prints some images on paper and check the registration of the colors on the paper. Depending on whether there is overlap or a gap, the operator changes the vertical positioning of the colors of the image on the paper by rotating and changing the relative positions of either one or both of the color plate cylinders with respect to the blanket cylinder to correct the misalignment of the colors. This is a time-consuming, tedious operation which requires a high degree of skill on the part of the operator.
Various devices are known for correcting misregistration of the colors printed by multicolor presses. There are two main categories of devices, those which align the plate cylinders and those which align the plates on the plate cylinders.
Patents which disclose devices for alignment of plate cylinders in multicolor presses include U.S. Pat. No. 2,172,279 (Hamilton, Jr.) which uses arcuate slots to provide for adjustable rotation of the print cylinders; U.S. Pat. No. 2,602,237 (Navarre) which uses a glass plate and transparencies to line up coaxial printing cylinders; U.S. Pat. No. 3,969,826 (Ottenhues et al.) which discloses a gauge and a method for lining up plate cylinders or presses with multiple color stations; U.S. Pat. No. 4,321,869 (Jeschke, et al.) which discloses a drive with a gear train for alignment and keeping cylinders in synchronization; and, U.S. Pat. No. 5,075,980 (Kerman) which discloses an alignment plate for lining up plate cylinders which can be removably attached to the press.
Patents which disclose devices and instruments for alignment of plates mounted on the print cylinders of multicolor presses include U.S. Pat. No. 1,067,067 (Schlueter, et al.) which discloses a built-in plate registering device for multicolor presses; U.S. Pat. No. 1,160,579 (Connelly) which discloses a removably attached gauging device to adjust the plates; U.S. Pat. No. 2,641,181 (Leeberg) which discloses a gauge device successively mounted on printing cylinders to multistation color presses for plate positioning; U.S. Pat. No. 3,090,129 (Gifford) which discloses a bracket which supports a transparent sheet for positioning plates on cylinders; and, U.S. Pat. No. 4,450,629 (Force) which discloses a removable attachment for horizontally aligning plates.
Although the above devices assist the operator in obtaining proper registration of the colors, there is clearly a need for an apparatus which enables the operators of two-color presses to rapidly and efficiently obtain proper color registration for their production runs and which is inexpensive, easy to manufacture, and easy to use.